[CMake] cmake 3.12 - python libs / 32 / 64 bits

[Eric Noulard]

Le jeu. 15 nov. 2018 à 09:47, Stéphane Ancelot <sancelot at numalliance.com> a
écrit :

> I agree. That was a debug snippet...but is wrong ... I setted up again the
> toolchain, but does not help.
>

If you are using a proper toolchain for 32bit compilation.
It looks like a bug in the find_package for Python in the cross-compiling
case.
Do you have a stripped down example which exhibit the issue?
Which version of CMake are you using?


>  So, I know where are include_dirs and libs  for 32 bits cross compiling,
> I have to hardcode it like this ?
>
>  add_library(python SHARED IMPORTED)
>  set_target_properties( python PROPERTIES IMPORTED_LOCATION /usr/lib32/
> libpython2.6.so )
>  target_include_directories(python SYSTEM ...
>

I think you can do that but it replaces the use of find_package(Python2
COMPONENTS Development)
may be fixing this would be a better long-term solution ?



>
>
> Le 14/11/2018 à 17:53, Marc CHEVRIER a écrit :
>
> The way you proceed is wrong.
> The system configuration is determined during the 'project' function call.
> Setting information after this call is useless. So, in your example, on a
> 64bit system, the compilation configuration will be 64bit (variable
> CMAKE_SIZEOF_VOID_P has value 8).
> This explain why 'FIND_LIBRARY_USE_LIB32_PATHS' has no effect. This
> property is taken in consideration only on 32bit systems.
>
> Moreover, I am not sure that modifying variable 'CMAKE_SYSTEM_PROCESSOR'
> is a valid action.
>
> To configure a 32bit compilation environment, two possibilities:
> * using environment variables: env CFLAGS=-m32 CXXFLAGS=-m32 cmake ...
> * using a toolchain file: see
> https://cmake.org/cmake/help/v3.13/manual/cmake-toolchains.7.html
>
>
> Le mer. 14 nov. 2018 à 14:06, Stéphane Ancelot <sancelot at numalliance.com>
> a écrit :
>
>> Hi,
>>
>> My system is 64 bits but I can cross compile python c modules for 32 bits
>> .
>>
>> Unfortunately I don't manage to retrieve python 32 libs , always the 64
>> bits version is found.
>>
>>
>> here is what I tried :
>>
>> cmake_minimum_required(VERSION 3.10)
>> project(py_autom)
>>
>>
>> set(CMAKE_SYSTEM_PROCESSOR "i686")
>>
>> set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -m32" CACHE STRING "c++ flags")
>> set(CMAKE_C_FLAGS   "${CMAKE_C_FLAGS} -m32" CACHE STRING "c flags")
>>
>> set_property(GLOBAL PROPERTY FIND_LIBRARY_USE_LIB32_PATHS TRUE)
>> set_property(GLOBAL PROPERTY FIND_LIBRARY_USE_LIB64_PATHS FALSE)
>>
>> include_directories(python2.6)
>> find_package(Python2 COMPONENTS Development)
>>
>>
>>
>> message(STATUS "python ${PYTHON_INCLUDE_DIRS} ${Python2_LIBRARIES_DIR}
>> ${Python2_FOUND}")
>>
>> Regards
>>
>> Steph
>> --
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-- 
Eric
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